MicroPython FaceBot

Welcome to the FaceBot Lab

Monty waving welcome Robots are much more fun when they have faces! In this lab you will draw simple emoji-style faces on the OLED display on the front of your robot. You can even give your robot different expressions depending on what it is doing. Let's build something amazing!

What Is the FaceBot?

The FaceBot is a robot that displays cartoon faces on a small OLED screen mounted at the front. The faces change to show the robot's "mood" or state:

Happy face — when the robot is driving normally
Surprised face — when it detects an obstacle
Sleeping face — when the robot is idle

We are inspired by the expressive faces on robots like Cozmo:

What You Need

Part	Purpose
Maker Pi RP2040 robot	The base robot with motors and controller
128×64 OLED display (I2C)	Shows the face — connect to the Grove I2C port
`ssd1306.py` driver	Library for drawing on the OLED

Make sure the ssd1306.py driver file is saved on your Pico before running any code. You can find it in the src/drivers/ folder of this project.

Setting Up the OLED Display

The OLED connects to the I2C Grove port on the Maker Pi RP2040:

OLED Pin	Maker Pi RP2040
GND	GND
VCC	3.3 V
SDA	GP0 (I2C SDA)
SCL	GP1 (I2C SCL)

Drawing a Happy Face

The OLED screen is 128 pixels wide and 64 pixels tall. You draw faces using circles, lines, and filled rectangles.

from machine import Pin, I2C
from ssd1306 import SSD1306_I2C
import time

# Set up the I2C bus and OLED display
i2c = I2C(0, scl=Pin(1), sda=Pin(0), freq=400000)
oled = SSD1306_I2C(128, 64, i2c)

def clear():
    """Clear the screen."""
    oled.fill(0)

def show_happy_face():
    """Draw a happy face in the center of the screen."""
    clear()
    # Outline of the head (circle approximated with an ellipse using lines)
    for x in range(30, 99):
        oled.pixel(x, 5, 1)   # top arc
        oled.pixel(x, 58, 1)  # bottom arc
    for y in range(5, 59):
        oled.pixel(29, y, 1)  # left side
        oled.pixel(98, y, 1)  # right side

    # Eyes — two small filled rectangles
    oled.fill_rect(44, 18, 8, 10, 1)  # left eye
    oled.fill_rect(76, 18, 8, 10, 1)  # right eye

    # Smile — a curved line using individual pixels
    for x in range(0, 30):
        # parabola curve for the smile
        y = int(0.03 * (x - 15) ** 2 + 38)
        oled.pixel(49 + x, y, 1)

    oled.show()  # send the drawing to the screen

show_happy_face()

Key Idea

Monty thinking oled.fill(0) sets every pixel to black (off). oled.pixel(x, y, 1) turns one pixel white (on). oled.show() sends the whole drawing to the screen at once — nothing appears until you call show().

Drawing a Surprised Face

def show_surprised_face():
    """Draw a surprised open-mouth face."""
    clear()
    # Head outline (same as happy face)
    for x in range(30, 99):
        oled.pixel(x, 5, 1)
        oled.pixel(x, 58, 1)
    for y in range(5, 59):
        oled.pixel(29, y, 1)
        oled.pixel(98, y, 1)

    # Wide round eyes
    oled.rect(42, 16, 12, 12, 1)  # left eye outline
    oled.rect(74, 16, 12, 12, 1)  # right eye outline

    # Round open mouth
    oled.ellipse(64, 46, 10, 8, 1)  # open-mouth oval

    oled.show()

Drawing a Sleeping Face

def show_sleeping_face():
    """Draw a sleeping face with closed eyes."""
    clear()
    # Head outline
    for x in range(30, 99):
        oled.pixel(x, 5, 1)
        oled.pixel(x, 58, 1)
    for y in range(5, 59):
        oled.pixel(29, y, 1)
        oled.pixel(98, y, 1)

    # Closed eyes — horizontal lines
    oled.hline(42, 23, 12, 1)  # left eye (closed)
    oled.hline(74, 23, 12, 1)  # right eye (closed)

    # Small straight mouth
    oled.hline(54, 44, 20, 1)  # neutral mouth

    oled.show()

Animating the Faces

Put the faces together with motor commands so the robot changes expression based on what it is doing:

import time

# Show sleeping face while waiting to start
show_sleeping_face()
time.sleep(2)

# Show happy face while driving
show_happy_face()
# ... motor drive code goes here ...
time.sleep(3)

# Show surprised face when obstacle detected
show_surprised_face()
# ... obstacle avoidance code goes here ...
time.sleep(1)

# Back to happy
show_happy_face()

Monty's Tip

Monty giving a tip Try adding a winking face by drawing only the right eye closed. You can also use oled.text("HI!", 48, 28, 1) to add a speech bubble with a word on the screen!

You Can Do This!

Monty encouraging Drawing faces with individual pixels takes a bit of patience. If your face looks wrong at first, try changing the x and y coordinates a little at a time. That is exactly how game artists work!

Great Work!

Monty celebrating Your robot can now show emotions! Try combining the FaceBot code with the collision avoidance robot so the face automatically changes when the robot spots an obstacle.